Many wireless communication technologies have been introduced for high-speed mobile communications.
Cooperatively, cells are getting narrower in radius to support high-speed communications and more telephony communications. Here, it is expected that employment of a centralized architecture using the current wireless network architecture is unable. Accordingly, the next generation communication system should be dispersively controlled and actively deal with environmental changes such as addition of a new base station.
To this end, a multi-hop cellular system has been proposed.
FIG. 1 illustrates a multi-hop cellular system according to the related art.
As shown in FIG. 1, one or more terminals 11, 12 and 13 are present within a coverage area of a base station 30.
Here, one or more specific terminals of the one or more terminals 11, 12 and 13 may operate as a relay. A terminal operating as the relay is in a good channel circumstance and has a high channel gain on the average.
That is, if a terminal present in a good channel circumstance operates as a relay, another terminal present in a bad channel circumstance may execute data transmission and reception with the base station via the terminal operating as the relay.
The method of utilizing a terminal as a relay in the cellular system allows improvement of transmission performance. That is, a terminal functioning as a relay may amplify a data signal to forward to each receiving end such that terminals located within a base station coverage can communicate with the base station more stably, resulting in improvement of the transmission performance.
As such, to decide whether to render a specific terminal operate as a relay, there are been algorithms, such as a centralized routing related to a direct decision by a base station and a distributed routing related to a decision by the terminal itself.
The centralized routing is an algorithm in which a base station receives channel gain information fedback from terminals and made a decision so as to notify each terminal of the decision. To this end, each terminal periodically informs channel information thereof, channel information relating to the base station and channel information between each terminal and the base station.
However, upon employing the centralized routing algorithm, the base station should be fedback incredibly a lot of channel information from terminals, and suffers from a huge load upon calculation of the fedback channel information. If the base station randomly makes a decision without feedback of the channel information, a gain by virtue of the centralized routing is rarely expected.
Hereinafter, the distributed routing will be described with reference to FIG. 2.
FIG. 2 is an exemplary view illustrating a distributed routing in the multi-hop cellular system according to the related art.
As shown in FIG. 2, the distributed routing is configured such that each terminal independently decides whether to function as a relay.
If the base station measures channel gains between terminals and the base station and broadcasts it to the terminals, each of the terminals randomly decides whether to function as a relay. Each terminal has its own relay probability, which is decided based upon channel gain information sent from the base station and a data rate of a packet to be sent.
However, upon employing the distributed routing, since the base station has already known such channel information, there is no need to perform the distributed routing. In addition, each of the terminals performs routing without knowing channel information relating to the other terminals, which causes a blind routing. Accordingly, such situation gives limitations of the gain.